1. Field of the Invention
This invention relates to coaster and three-speed bicycles, and in particular, to bicycles having bevel gears and one or more drive shafts that replace the traditional spur gears and chain.
2. Description of the Related Art
Traditional coaster or 3-speed bicycles have gears that are changed internally within the hub. Motion from the pedals is transferred to the rear wheels by means of a chain that extends around a sprocket in the pedal area and around a smaller sprocket at the center of the rear wheel.
A number of problems may be associated with these bicycle chains. They are subject to slippage if the length of the chain is not correctly adjusted such as on ten speed derailleurs. Because the chains are often at least partially exposed, clothing, grass, or other objects may become caught in the chains as the chains move past the objects. In addition, dirt and foreign matter can become lodged on the chain links and decrease the efficiency of the chain mechanism. The chain and sprocket mechanism also must be frequently to keep it moving smoothly.
Other types of drive mechanisms have been designed to try to avoid the problems presented by the traditional chain mechanism. For example, in the reciprocating powered bicycle, reciprocating motion instead of rotary motion causes the motion of the pedal to be transferred to the motion of the wheel (U.S. Pat. No. 4,019,230). The bicycle is powered by the use of two roller clutches or ratchets, wherein each is driven by means of one pedal through a portion of a stroke only. In this bicycle, the pedals which are interconnected, are about 90.degree. apart, instead of the traditional 180.degree..
The bicycle in U.S. Pat. No. 599,048 uses a chain and drive shaft together. In this bicycle a windwheel is mounted forward of the handlebars. Movement of the bicycle by pedalling using a standard sprocket and chain arrangement causes the windwheel to rotate. This rotation causes a shaft to revolve, which in turn causes a beveled gear wheel at the rear wheel to turn to aid in propelling the bicycle. There are still potential problems that are associated with the moving, exposed chain present in this invention.
Another type of bicycle has a variable speed ratio transmission mounted on a bracket connected to the rear axle of the bicycle. It utilizes a flexible V-belt for transmitting rotary motion between a drive pulley of the transmission, and a driven pulley (U.S. Pat. No. 4,741,546). Such a belt also has the problems associated with a long, exposed moving part as are present with the chain of the traditional bicycle, and in addition, this bicycle design retains a number of chains for transmitting torque from the drive pulleys.
Another pedal bicycle with power take-off employs a drive shaft having an axis of rotation radial to a casing and a pedal shaft extending through the casing, such that rotation of the pedals causes the draft shaft to turn and a drive sprocket for a chain to turn. The drive shaft is used to drive a battery-operated motor-generator or a battery charger, or is used to provide power for a bicycle lighting system (U.S. Pat. No. 3,910,126).
In some cases drive shafts have been used with certain motorcycles such as the BMW motorcycle, which may have a single drive shaft. Plural drive shafts have not been used on two-wheeled non-motorized vehicles in a manner to provide an efficient, durable bicycle without a bicycle chain.
It is therefore an object of this invention to provide a bicycle having a means of linear transmission from the pedals to the hub of the bicycle for better efficiency and speed ratios than prior bicycles.
It is a further object of this invention to provide a solution to chain slippage problems by utilizing fewer mechanical parts.
It is also an object of this invention to provide a self-lubricating transmission system that is solid in construction.
It is a further object of this invention to provide a bicycle with a mechanical advantage based on gear and ratio modifications.
Other objects and advantages will be more fully apparent from the following disclosure and appended claims.